The invention relates to a method of brush plating chrome on a substrate. In particular, the invention relates to a method of brush plating chrome that employs a tank chrome solution in the plating process.
Tank plating and brush plating are two well known techniques for plating the surface of a substrate with a plating material. In tank plating, the substrate to be plated is entirely emersed in a tank of plating solution and a plating current is passed through the substrate and the tank plating solution in order to electroplate a plating material, for example chrome, on the surface of the substrate. The entire exposed surface of the substrate is plated to a uniform thickness during the tank plating process. In contrast, brush plating is commonly employed to plate specific surface areas of the substrate. For example, brush plating has been employed to repair scratched or damaged areas of a previously plated surface. In brush plating, a plating solution is supplied to a hand-held anode that is passed over the surface of the area to be plated. As the anode is passed over the surface of the substrate, the plating solution is dispensed and a plating current is passed through the anode to the grounded substrate.
However, the use of brush plating to repair damaged chrome surfaces has not met with satisfactory results. Typically, the repaired area did not blend well with the unrepaired surface producing a visibly undesirable result. Problems with adhesion to the substrate were also experienced. Methods have been developed to address some of the aforementioned problems (See, for example, U.S. Pat. Nos. 3,751,343, 3,393,134, 3,313,715), however, these methods require the use of specialized brush plating solutions rather than the standard solutions used in tank plating methods.
In the area of chrome plating specifically, the specialized brush plating solutions require the use of sodium hydroxide and trivalent chromium in order to achieve adequate results. Another typical characteristic of specialized brush plating solutions is the use of a higher metal ion concentration than that employed in tank solution. As a result, the specialized brush plating solutions are typically more expensive than tank plating solutions. In addition, the aforementioned methods required that the area to be plated to be activated with a thin deposit of nickel. The requirement for a separate special brush plating solution to repair parts also results in additional expenses being required for double stocking two solutions.